Substrate(s) with an ultra-flat metal surface is/are important in two-dimensional materials research and in nano-structure fabrication, such as, for example, especially in formation of self-assembled monolayers (SAM's). In these applications, the substrate surface roughness dominates the nano-structure and hence the properties of the materials deposited and/or formed on the substrate surface.
Currently available techniques to prepare flat metal surfaces include electron-beam physical vapor deposition, chemical-mechanical polishing, template-stripping, and thermal annealing. Electron-beam physical vapor deposition involves direct physical vapor deposition (PVD) of an evaporated metal where control of the evaporation rate, and hence grain growth, can be used to control the roughness of the deposited material.
Chemical-mechanical polishing involves polishing a substrate surface wherein a slurry of an etchant is used to remove surface asperities.
Template stripping embodies evaporation of a metal onto an ultra-flat template surface followed by lift-off using an attached support to free the deposited metal layer for further use.
Thermal annealing is used to induce atom mobility and hence minimize grain boundaries of deposited material and can be used together with other techniques, such as template stripping, to provide smooth flat substrate surfaces.
However, there is a need for a method for preparing an ultra-flat metal surface that is improved over existing techniques. Since surface morphology affects the performance and structure of such devices, there also is need for surfaces whose roughness can be readily tuned and their morphology (defect density, mechanical properties, grain sizes, defect types, defect sizes) are controlled.